In normal operation of subterranean tools shifting of components to reconfigure a tool for removal or for other tasks has the result of initiating substantial acceleration of one part with respect to an adjacent part until a supported travel stop is encountered which produces high impact shock loading as the acceleration and velocity comes to a stop. In some applications the relatively moving components are not sufficiently centralized and this lack of centralization can create angular misalignment at the impact location. The result of such offset impacts is difficulty in redressing the tool for subsequent use and, in extreme cases component damage to threads or adjacent structures.
Shock absorbers are used in a variety of applications. One unique issue in subterranean tool applications is the extremely confined environments in which components have to be mounted and supported. Typically shock absorbers where space is not an issue are telescoping structures where fluid is displaced through an orifice at a predetermined rate to reduce velocities before impact. Some of these designs incorporate shear pins that break to allow the shock absorber to do its job. Some example of various applications for shock absorbing systems are U.S. Pat. No. 3,913,963 (motor vehicle); U.S. Pat. No. 3,767,142 (flare parachute); U.S. Pat. No. 7,484,905 (traffic control bollard); U.S. Pat. No. 7,530,759 (traffic barrier) and U.S. Pat. No. 4,300,364 (overload coupling). In some designs the spring provides a lost motion feature that protects a pivot pin such as U.S. Pat. No. 5,645,208 (spring 119 and pin 128). Other designs in subterranean applications involve plastic deformation by a wedge as a shock absorbing mechanism as illustrated in U.S. Pat. No. 6,109,355. Some downhole shock absorbing devices are illustrated in U.S. Pat. No. 4,232,751 (FIG. 2b items 57 and 55); U.S. Pat. No. 4,074,762 (FIG. 5) and U.S. Pat. No. 4,317,485 (items 54 and 60).
FIGS. 6c and 7c of US 2014/0196890 represent a known tool for setting a liner hanger using a movable sleeve that allows the closing of a flapper that has a rupture disc in the flapper. After the slips are set and the flapper sleeve is shifted to allow pressure buildup to set the liner hanger seal after the liner hanger slips are earlier set for support. At a predetermined pressure the rupture disc is failed and the running tool is removed. This tool addressed an issue of developed backpressure in the running tool due to rapid removal causing backpressure at the ruptured disc and thus unintentionally pushing out the running tool slips for another bite which would impede removal of the running tool. Other than simply slowing down the tool speed during removal, this design opened a port when the flapper sleeve shifted to put the running tool slips in pressure balance so that the developed backpressure during tool removal did not create an unbalanced force on the running tool slips to allow rapid removal of the running tool. The problem with this tool is that in response to pressure application to set the liner hanger seal and release the running tool there was a severe impact between radial surfaces 108 and 114 that was not always a concentric impact which, as described above, created issues of redressing the tool for another use and could even cause component damage requiring part replacement. Thus the present invention was inspired by the need reduce such impact loading that could often be at an angular impact due to component misalignment during relative movement.
One objective of the present invention is to absorb high kinetic energy within a tool by using a collet style load ring that behaves like a spring and introducing shear screws by strategically placing them to reduce the high impact velocity, which ultimately reduces the kinetic energy and the impact load on the tool. In one use, the invention pressure balances the anchor of the TORXS® running tool offered by Baker Hughes Incorporated, as shown in US 2014/0196890 but further absorbs high impact loads without transmitting them through the tool's threaded connections and thin cross-sectional areas. High impact load can damage threaded connections by stripping or jumping the start of the threads which makes it difficult to disassemble the tool.
During a recent laboratory test conducted on a 7″ TORXS balanced anchor design as shown in US 2014/0196890, when pressure was applied to shear the screws and move the sleeve axially to open cylinders and balance the anchor, high impact load caused damage to the threaded connection due to axis misalignment and high kinetic energy. A torque machine was used to break the connections where torque value observed was as high as 3000 ft-lb. The threads were damaged which prevented reuse of the parts. The high impact load was generated due to motion of tool components with high kinetic energy after shearing of a primary shear screw at design pressure. This high kinetic energy, if not absorbed, can cause failure of the tool due to high impact loading through the tool joint and thin cross-sectional areas thus causing bearing failures and tool joint damage due to stripping of threads or jumping of start of threads.
The preferred embodiment of the present invention encompasses a collet style load ring which behaves like a spring when engaged. It absorbs high impact energy by transmitting the load in tension through the collet and dissipates part of the load when the collet collapses thus being a load absorber for this application. The design centralizes the tool before and after impact because of a proper supporting scheme. In addition to primary shear screws, there are secondary shear screws that are strategically placed in multiple rows such that when the tool starts moving with high kinetic energy, the second row of shear screws shears and minimizes the velocity of the tool in motion. The third row of shear screws helps to align the collet with the locating shoulder on the lower connector where the collet engages. Third row shear screws also keeps the two parts axially locked to each other with the help of the balancing sleeve above it. The last shear sequence, i.e. third row of shear screw, shear just before the collet engages the lower connector shoulder thus dampening the impact load further. Another advantage is that if the collet style design ever failed then there is a secondary containment mechanism to take the impact load and hold the tool in place without losing it down hole. This is done with the help of the balancing sleeve that is on the outside of the collet mechanism. Other shock absorbing applications in subterranean tools are contemplated. Those skilled in the art will appreciate these and other aspects of the present invention from a review of the preferred embodiment of the invention and the associated drawings while recognizing that the full scope of the invention is to be found in the appended claims.